Mixers may be employed in a wide variety of electronic systems. For example, mixers may be used for frequency conversion in a variety of systems including radio systems. Examples of mixing devices that may be employed in a mixer include varieties of field effect transistors (FETs) and bipolar junction transistors (BJTs).
A mixing operation in a mixer may include periodically switching a mixing device between its two conductions states. For example, an FET or BJT mixing device may be periodically switched between its on state and its off state during a mixing operation.
A mixing device may be switched between its on and off states by applying a periodic drive signal to a control terminal of the mixing device. For example, a sine wave or square wave drive signal may be applied across the gate and the source of an FET mixing device to periodically switch the FET between its on and off states. Similarly, a sine wave or square wave drive signal may be applied to across the base and the emitter of a BJT mixing device to periodically switch the BJT between its on and off states.
A control terminal of a mixing device may exhibit electrical characteristics that hinder the switching of the mixing device between its on and off states. For example, the gate of an FET or the base of a BJT may have a characteristic capacitance. The characteristic capacitance of a mixing device may rise as the voltage on the control terminal of the mixing device rises toward a threshold voltage level that switches the mixing device to its on state. The rising characteristic capacitance may limit the speed at which a mixing device may be switched between its on and off states, thereby increasing the time that the mixing device is in an intermediate state between its on and off states. Unfortunately, an increase in the amount of time spent in an intermediate state between its on and off states may cause a mixing device to exhibit an increase in signal loss and signal distortion.